This invention relates to new 2-substituted-amino-5-methyl-phenol compounds and compositions containing these compounds as primary intermediates for oxidative coloring of hair fibers.
Coloration of hair is a procedure practiced from antiquity employing a variety of means. In modern times, the method most extensively to color hair is an oxidative dyeing process utilizing one or more oxidative hair coloring agents in combination with one or more oxidizing agents.
Most commonly a peroxy oxidizing agent is used in combination with one or more oxidative hair coloring agents, generally small molecules capable of diffusing into hair and comprising one or more primary intermediates and one or more couplers. In this procedure, a peroxide material, such as hydrogen peroxide, is employed to activate the small molecules of primary intermediates so that they react with couplers to form larger sized compounds in the hair shaft to color the hair in a variety of shades and colors.
A wide variety of primary intermediates and couplers have been employed in such oxidative hair coloring systems and compositions. Among the primary intermediates employed there may be mentioned p-phenylenediamine, p-toluenediamine, p-aminophenol, 4-amino-3-methylphenol, N,N-bis(2-hydroxyethyl)-p-phenylene diamine, 1-(2-hydroxyethyl)-4,5-diaminopyrazole and as couplers there may be mentioned resorcinol, 2-methylresorcinol, 3-aminophenol, 2,4-diaminophenoxyethanol, and 5-amino-2-methylphenol.
There are numerous additional requirements for oxidation dye compounds that are used to dye human hair besides the color or the desired intensity. Thus, the dye compounds must be unobjectionable in regard to toxicological and dermatological properties and must provide the desired hair color with a good light fastness, good selectivity, fastness to a permanent wave treatment, acid fastness and fastness to rubbing. The color of the hair dyed with the dye compounds in each case must be stable for at least 4 to 6 weeks to light, rubbing and chemical agents. Furthermore, an additional requirement is the production of a broad palette of different color shades using different developer and coupler substances.
For providing a yellow or orange yellow coloration to hair, resorcinol and 2-methyl resorcinol have been extensively used in combination with p-aminophenol. Coupling of p-aminophenol with 2-methyl resorcinol provides weak orange yellow, while coupling of p-aminophenol with resorcinol gives weak yellow green. 6-Amino-m-cresol (U.S. Pat. No. 4,396,392) as well as direct dye 2-amino-4-nitro-6-chlorophenol is also used in current practices. A combination of tetraaminopyrimidine and 3,4-dimethyl-2,6-dihydroxy pyridine (EP 63736 A2) or a combination of 6-hydroxyindole and p-aminophenol (U.S. Pat. No. 5,279,620) are also used. 6-Hydroxyindole couples with p-aminophenol and p-phenylenediamine to provide golden beige and medium golden brown, respectively. However, these yellow couplers suffer from weak and dull coloration, especially in the presence of primary intermediates and couplers. Therefore, there is a need to develop more compounds for providing reliable yellow and orange yellow coloration in oxidative hair coloring.
It is therefore an object of this invention to provide new primary intermediate compounds useful for providing yellow or orange yellow color shades with various combinations of primary intermediates and couplers.
It has been discovered that new 2-substituted-amino-5-methyl-phenol compounds are suitable primary intermediates for hair coloring compositions and systems for providing good oxidative coloration of hair and for providing acceptable light fastness, good selectivity, fastness to shampooing, fastness to permanent wave treatment, and suitable for providing a wide variety of different color shades with various primary intermediate and coupler compounds.
The invention provides new 2-substituted-amino-5-methyl-phenol compounds of Formula (1): 
wherein R is selected from C1 to C5 alkyl or hydroxyalkyl, a C3 to C6 cyclic ring containing hetero atoms selected from O, S and N atoms, and xe2x80x94CH2xe2x80x94Ar where Ar is an aromatic ring wherein the aromatic ring may be substituted with one or two hydroxy, C1 to C3 alkoxy, or amino groups.
These novel primary intermediates are used to provide coloration to hair in which there is good dye uptake by the hair and provides shades or colors that are stable over a relatively long period of time. The novel primary intermediates provide for dyeing of hair to impart color or shades that possess good wash fastness, good selectivity, and do not undergo significant changes on exposure to light, perspiration or shampooing.
The 2-substituted-amino-5-methyl-phenol compounds of this invention are those of formula (1) 
wherein R is selected from C1 to C5 alkyl or hydroxyalkyl, a C3 to C6 cyclic ring containing hetero atoms selected from O, S and N atoms, and xe2x80x94CH2xe2x80x94Ar where Ar is an aromatic ring wherein the aromatic ring may be substituted with one or two hydroxy, C1 to C3 alkoxy, or amino groups.
Preferably, R is C1 to C3 alkyl, benzyl, thiophen-ylmethyl and pyrrolylmethyl.
The new 2-substituted-amino-5-methyl-phenol compounds of formula (1) of this invention can be prepared according to the following reaction sequence wherein R is as defined herein before. 
In this synthesis the new 2-substituted amino-5-methyl-phenol compounds of formula (1) of this invention can be prepared by reaction of 5-methyl-2-nitro-phenol of formula (2) with a benzyl halide, such as benzyl bromide, in the presence of potassium carbonate in dimethylformamide (DMF) to produce the compound of formula (3), and catalytically hydrogenating the compound of formula (3) with Pd/C at about 60 psi hydrogen to provide a compound of formula (4) which is reductively aminated with a compound of the formula RCHO or a C3 to C6 cyclic ring ketone and reducing agents, such as LiAlH4, DIBAL-H, NaBH4, sodium triacetoxyborohydride, zinc borohydride, sodium cyanoborohydride, zinc acetate and polymethylhydrosiloxane (PMHS/Ti(O1Pr)4 to produce a compound of formula (5) and catalytically hydrogenating the compound of formula (5) to provide a compound of formula (1).